Caged electron gun



United States Patent 3,291,638 CAGE-i1 ELEtlilRON GUN Herbert Louis Levin, Paterson, Ni, assignor to International Telephone and Teiegraph Corporation, Nutley, NJL, a corporation of Maryland page Aug. so, 1%.2, Ser- No. sensor in Claims. {8. 3l3-25 This invention relates to an improved structure for a traveling wave type tube and particularly to a novel electron gun assembly therefore which is easily and accurately aligned and secured in a desired position.

The positioning of the electron beam in a traveling wave tube to interact with the electromagnetic wave along the slow-wave helix structure, is highly critical. The beam must be very accurately aligned along the tube axis within the helix in order to provide proper operation with minimum distortion and long life. For best ciliciency, the beam should be as close to the helix as possible without interception, as impingement of the beam on the helix can cause burning and gassy operation. In addition, a simplified assembly of the various beam forming elements in a fixed longitudinal and radial relationship permits the use of mass production techniques.

Prior art devices have utilized a plurality of highly precise annular insulator spacers between electrodes in conjunction with complex appendages on the electrodes to engage and align the various elements. A number of special springs were also required to hold the entire assembly together. In another electron gun support, slotted rods were used to secure individual electrodes in only an axial direction. There also was no simplified unitary construction and assembly was relatively diiiicu-lt and costly.

It is therefore the primary object of the present invention to provide an improved simplified electron gun structure.

Another object is to provide a novel structure for accurately aligning and spacing the electrodes of the gun with respect to each other and to the helix, in both radial and longitudinal positions. These objects are achieved by use of a caged electrode assembly structure which is secured to a set of slotted support rods. The rods and slots engage cut-outs in the cathode support flanges and electrodes to determine the positions of the various elements. The details of the invention will be more fully understood and other objects and advantages will become apparent in the following description and accompanying drawings wherein:

FIG. 1 is a longitudinal fragmentary sectional view of a tube showing the novel electron gun assembly;

FIG. 2 is an end view of the flange element of the cage structure, shown independently;

FIG. 3 is a cross-sectional view, taken along lines 3-3 of FIG. 1 and shows an anode element;

FIG. 4 is a view of a slotted rod utilized in the novel structure; and

FIG. 5 shows a fragmentary sectional view of another form of the slotted rod and engaging electrode.

As shown in FIG. 1, a precision glass envelope or bulb encloses the electron gun assembly of a traveling wave tube. Ceramic rods 12 bear on the inner surface of the envelope and support a metallic spool-shaped cage structure 14. A predetermined minute spacing between the rods and envelope provides for expansion under heat. The envelope and rods thus align the cage structure with respect to the helix, not shown. The outer portion of the cage is formed of a cathode support 16 and a mating flange element 18. Notches, indentations or cut-outs 20 in the transverse ends of the flange element 18, as shown independently in the end view of FIG. 2, and like periph- Bidlfidh Patented Aug. 1?, 3%65 six eral notches in the cathode support 16, fit around the rods beyond the widest dimension thereof and thus prevent peripheral or radial movement with respect to the rods. The extreme outer portions of the metal flange and cathode support are spaced from the glass to prevent difliculties which may be caused by expansion from RF. heating of the gun for out-gassing the tube during the exhaust operation and also to eliminate localized hot spots which can crack the glass. The cathode 22 forms the inner portion of the gun assembly with a transverse heater shield 24 at one end and a hollow beam forming coated electrode 26 at the other end. An intermediate tubular heat reflecting shield 28 surrounds the cathode and is connected to the cathode support 16. An opening 39 and out-gassing passage 32 are formed in support 16 by a lanced indented area and the inner surface of the lanced area is used to align and support the heat shield 28. The necked port-ion of support 16 is com nected to the lower portion of the cathode and to heater shield 24. A heater and tube stem of known form, not shown, are positioned below this shield.

A series of shallow transverse slots or segments 34 are out at predetermined locations along each of three rods, one of which is shown in FIG. 4. The slotted rods are of the type more fully described in Pat. No. 2,943,227, issued June 28, 1960, to the instant inventor. Into these slots are inserted the peripheral ends of the respective sheet metal electrodes of the electron gun such as a focus electrode 36, shown adjoining cathode support 16, a grid 3% and an anode 40. The cross-section of FIG. 3 shows another view of the arrangement of anode 4% with respect to the rods. The anode is of a triangular form with rounded edges 42 adjacent the rods. The clearance between the straight sides and the glass envelope is utilized for leads and getter structures which may be required. Cut-outs 44 formed in the edges have rounded sides 46 to accommodate a peripheral portion of the rods and a flat bottom 48 to engage the corresponding slots in the rods. Some clearance is provided between the mating bottom slotted portions of the rod and flat portions 53 of the electrodes so that this dimension, which is difiicult to obtain with precision, is not critical. To obtain radial alignment, however, finger-like bosses or lanced members 59 are struck through the anode plate adjacent the round innermost surface of the rod close to the slot. The cut outs thus permit the bosses to bear on the rods. The bosses, also orient the gun elements with respect to the rods and provide a fixed radial position, while the mating cut-outs and slots accurately align the elements axially and the rounded sides thereof prevent circumferential movement. The electron beam from cathode 26 can then properly flow through radial holes 52 in the anode and other electrodes and through a drift tube 5 shown adjoining the anode, before entering the helix as indicated, not shown. The helix is longitudinally spaced and insulated from the drift tube.

In assemblying the gun, the electrodes are placed in the slots of the rods and then the cage assembly, including the cathode and heat shield, is slipped onto the rods. The flange element 13 is then spot welded in a known manner to the adjacent gun element 16 at suitable points around the periphery, not shown, and thus locks all of the components together in a fixed position. The various other metal joints or connections are preferably also spot welded to form a unitary structure supported by the rods. Brazing operations are thus eliminated. Alternatively, to eliminate spot welding, retaining tabs can be formed on the side edges of the flange or gun elements which, when bent over a mating part, can lock the parts in place. In one form cut-outs 20 can be U-shaped with a rounded bottom and straight sides. Pointed tabs at the in the rod. In this instance bosses 50 are eliminated and the rods are held in radial alignment by the rounded edges 62 and can now be inserted more easily from a peripheral position.

It may thus be seen that the present invention provides a novel simplified electron gun structure which can be 5 accurately aligned and secured in a predetermined position. While only a single embodiment has been illustrated, it is apparent that the invention is not limited to the exact form or use shown and that many variations may be made in the particular design and configuration without departing from the scope of the invention as 'set forth in the appended claims.

What is claimed is:

1. An electron beam device comprising:

an envelope; 9

a plurality of longitudinal insulator rods positioned about the inner surface of said envelope, said rods having a plurality of spaced indentations; V

a plurality of transverse beam control electrodes spaced from said envelope surface and having peripheral cut-out portions engaging said rods and slots for axial, radial and circumferential alignment;

an electron beam forming cathode positioned coaxial with and adjacent said electrodes; and

a longitudinal cathode support cage surrounding said cathode and forming a unitary structure therewith, said cage comprising a cathode support having transverse ends spaced from said envelope surface and peripheral cut-outs at each end engaging said rods for circumferential alignment, said rods and envelope providing radial alignment for said cathode, cathode support and electrodes.

3; The device of'claim 2 wherein said cut-out portions of said electrodes are U-shaped, said rods being oriented so that one side of said cut-out engages said slots and the round bottom engages the surface of said rods.

4. The device of claim 2 wherein said electrodes and support ends are triangularly shaped and said cut-outs are at the corners thereof.

5. Thedevice 'of claim 3 wherein said cut-out portions include peripheral tabs extending, from the sides, said tabs adapted to be crimped around the circumference of from said envelope surface and having peripheral indentations engaging corresponding indentations in said rods for axial, radial and circumferential alignment;

an electron beam forming cathode positionedcoaxial with and adjacent said electrodes; and

a longitudinal cathode support cage surrounding said cathode and forming a unitary structure therewith, said cage comprising a cathode support spaced from said envelope surface and having peripheral indent-a tions at each end engaging said rods for circumferential alignment, said rods .and envelope providing radial alignment for said cathode, cathode support and electrodes. V

2. An electron beam device comprising:

an envelope;

a plurality of longitudinal insulator rods positioned about the inner peripheral surface of said envelope,

at predetermined intervals therea long;

i .a plurality of transverse beam control electrodes spaced 7 said rods.

6. The device of claim 4 further including lanced members formed in said electrodes adjacent said cut-out portions and engaging said rods.

7. The device of claim 4 wherein said cathode support includes a lanced'area forming an out-gassing'passage therethrough and a heat shield surrounding said cathode.

8. The device of claim 7 wherein said heat shield and cathode and support form a unitary structure supported on said rods. a

9. The device of claim 6 wherein said cut-out portions of'said electrodes have flat bottoms engaging said transverse'slots in said rods and round edges engaging the surface of said rods. Y

10. The device of claim 9 wherein said cathode support cut-outs are round and eugage'the surface of said rods beyond the widest dimension thereof.

References (Zited by the Examiner- UNITED STATES PATENTS 8/60 Rodriguez et al. 3153.5 X

GEORGE N. WESTBY, Primary Examiner. JOHN W. HUCKERT, Examiner. 

1. AN ELECTRON BEAM DEVICE COMPRISING: AN ENVELOPE; A PLURALITY OF LONGITUDINAL INSULATOR RODS POSITIONED ABOUT THE INNER SURFACE OF SAID ENVELOPE, SAID RODS HAVING A PLURALITY OF SPACED INDENTATIONS; A PLURALITY OF TRANSVERSE BEAM CONTROL ELECTRODES SPACED FROM SAID ENVELOPE SURFACE AND HAVING PERIPHERAL INDENTATIONS ENGAGING CORRESPONDING INDENTATIONS IN SAID RODS FOR AXIAL, RADIAL AND CIRCUMFERENTIAL ALIGNMENT; AN ELECTRON BEAM FORMING CATHODE POSITIONED COAXIAL WITH AND ADJACENT SAID ELECTRODES; AND A LONGITUDINAL CATHODE SUPPORT CAGE SURROUNDING SAID CATHODE AND FORMING A UNITARY STRUCTURE THEREWITH, SAID CAGE COMPRISING A CATHODE SUPPORT SPACED FROM SAID ENVELOPE SURFACE AND HAVING PERIPHERAL INDENTATIONS AT EACH END ENGAGING SAID RODS FOR CIRCUMFERENTIAL ALIGNMENT, SAID RODS AND ENVELOPE PROVODING RADIAL ALIGNMENT FOR SAID CATHODE, CATHODE SUPPORT AND ELECTRODES. 